Control system



A. L. HARVEY. CONTROL SYSTEM.

APPLICATION FlLED MAY 7, 1919.

Patented Apr. 11, 1922.

INVENTOR A/be/"f L. Harvey.

AT'TORNEY UNITED STATES PATENT OFFICE.

' mnm' L. HARVEY, or wrnxnwsnuno, PENNSYLVANIA, ASSIGNO-R TO wnsrme- 1nousn mmc'rnxc a mnurao'runme comranv, A oonronarron or 12mm-Toallwhom'itmaycomem: t i v Be it known that I, Amara -L. HARVEY, acitizen of the United States, and a resident of W ilkinsbur in thecounty. of Allegheny and'State of ennsylvania, have invented a Q new anduseful Improvement in Control Systems, of which the followingis aspecification.

My inventlon relates tomotor-control systems and particularly to'systemsfor'controllinfintermittentl operated motors.

intermittent yoperated compound or shunt-wound motors, provision must bemade for disconnecting the shunt fieldmagnet winding from the source ofenergy when 'the motor is at rest to prevent overheating and burning outof the winding.

If the motor 'is designed for dynamic-braking, however, the wmding mustbe maintained energized until the motor has come substantially m mt. I iO I o o The object of my invention 1s to provide an improvedmotor-control system for shunt or compound-wound motors which shallmsure the de-energiz'ation of the shunt fieldmagnet winding when themotor is at rest but the energization thereof during run- L ninganddynamic braking.

- connecte According tomy'invention, theshunt-fieldthe motor'has comepractically to rest.

In the accompanying drawing, which is a diagrammatic v ew of circuitsand apparatus embodying my invention, a compound wound motor, having anarmature 1, a series fieldmagnet winding 2 and a shunt field-. magnetwinding 3, is-connected to lin'econ ductors 4 and 5, which, in turn, areconnected to an suitable source of direct current.

I A contro er 6, which is here shown as of the "drum ty ,-is adapted toconnect the armae line conductors 4 and 5 and to effect theshort-circuiting of an accelerating resistor 7 which, is in series withthe armanormally disconnected fromthe line conductors-fl and 5 but isadapted to .be connected thereto by a relay 8*havingan ture'Lf Theshunt'field magnet winding 3 is energizing CONTROL SYSTEM.

i Specification of Letters Patent, Patented Apr, 11, 1922, Applicationfiled in; 7, 1919. Serial No. 295,290.

- winding 9, that is connected across a starting resistor 7, and asecond winding 10 that is connected across the armature 1.

Assuming the. controller 6 to be actuated,

for example, to the right, a circuit will be established from the lineconductor 4, through stationary'contact members 11 and 12, which arebridged by the drum controller 6, the series field-magnet winding 2, thearmature 1 and a stationary contact member 13 of the controller 6, by aconductor 14,

through the resistor 7 a stationary contact member 15 of thedrumcontroller 6, which,

i in thefirst position to the right of the drum controller 6, is inengagement with a movable contact member 16 and, through seg- .ment 17and stationary contact member 12?,

to the line conductor 5. The armature 1 1s thus connected to the lineconductors 4 and 5 in series with the field-magnet winding 2 and thestarting resistor 7. v

The closing of this circuit results in a flow of current through theresistor 7 so that the coil 9 becomes energized in accordance with thedrop in voltage across this resistor. The relay 8 becomes thereuponclosed to connsct the shunt field-magnet winding 3 to the lineconductors 4 and 5.

Further actuation of the controller 6 to the right will effect theshort-circuiting of successive portions of the resistor 7 until,

ultimately, the resistor becomes entirely short-circuited. The coil 9becomes thereby tie-energized, but the relay 8 is maintained in actuatedposition, to maintain the connection of the field-magnet winding 3 tothe line conductors 4 and 5, by the coil 10, which is energized inaccordance with the counterelectromotive force of the'motor TOStOPthemotor, the controllermay be actuated to the left, until it occupiesthe illustrated ofi sition, whereu on a cir cuitf is established fromone brush of the. armature 1, through contact members 13 and 19 and adynamic-braking resistor 20, to the other brush of the armature 1. Themotor may thus be dynamically-braked. During such braking, the coil 10is maintained energized, in accordance with the counter-electrm motiveforce of the motor, so that the fieldmagnet winding 3 is maintainedenergized until the motor comes substantially to rest, at which time therelayiwill become open by gravity to disconnect the winding 3 from theline conductors 4 and 5 and thereby protect the wmding 3 from possibleinjury from overheating while the motor is at rest.

The motor may be operated in the opposite direction by actuating thecontroller 6 to the left.

In accordance with my invention, the s hunt field-magnet winding of amotor is disconnected from the source of energy Whenever the motor is atrest but is connected thereto during normal operation and duringdynamic-braking'. Obviously, my invention is not restricted to thespecific details above illustrated and describedand I desire, therefore,that the appended claims shall be construed broadly, except in so far aslimitations may be specifically imposed therein;

I claim as my invention:

1. The combination with an electric motor having an armature and afield-magnet winding and a starting resistor in circuit with said motor,of means controlled in accordance with the drop in potential across saidresistor and across said armature for controlling said.

winding. v

2. The combination with an electric motor having an armature and a shuntfield-magnet winding and a starting resistor in circuit with said motor,of means controlled by the current traversing said armature andrthecircuit of said winding having an energizing coil connected across saidarmature.

In testimonywhereof, I have hereunto subscribed my name this 23d day ofA ril 1919.

- AIQVEY.

ALBERT L. H

resistor and said arma-

